1. Field of the Invention
The present invention generally relates to a method and apparatus for preventing contamination during a process flow.
2. Description of the Related Art
For mass-production consideration, the sequence of equipment used in a process flow must be well kept in order to avoid cross-contamination. For example, in a process flow for semiconductor wafers, an etch equipment used for patterning a metal layer can not be used to pattern a polysilicon layer during the same process flow. It is because that metals, typically Al or Cu, can induce localized energy states in the forbidden energy gap of the gate oxide to increase the gate leakage and therefore degrade the device performance. If a wafer A having a metal layer and a wafer B not having a metal layer are both processed in the same equipment, it is possible for the wafer B to acquire some metal atoms undesirably from the wafer A. Since the wafer B may contribute the metal atoms directly to equipment during the subsequent steps of the process flow, other wafers not having the metal layers are also at the risk of being contaminated by the metal atoms.
Although the process flows in many semiconductor manufacturing factories today are performed and monitored by automatic computer-controlled systems, such as a manufacture executive system (MES), the typical methods employed to prevent wafer contamination are still manually performed. For example, when a well-trained operator receives a cassette containing a plurality of wafers, he (or she) has to check out whether or not a special mark or tag indicating the presence of metal is thereon attached to the cassette in order to process the cassette with a proper action. If by any chance the operator omits the step to check the mark or label on the surface of the cassette and process it directly, a disaster of a wide-spread contamination among the processed wafers may occur.
Therefore, an object of the present invention is to provide a method and apparatus for preventing contamination automatically during a process flow.
In accordance with one aspect of the present invention, a method is provided as follows for finding contamination occurrence in a process flow according to the present invention. First of all, a tool database in which a plurality of tools are defined of xe2x80x9ctaggedxe2x80x9d by a set of contamination information of the tool database for being either a contaminated tool or an uncontaminated tool. Then a process database including the order of steps in the relevant process flow and a corresponding tool information for each step of the process is input to the computer. Said tool information includes at least one tool to be executed during the relevant step of the process flow without including the contamination information of each tool. Finally, the process database associated with the tool database is cross-examined in order to display a contamination warning message prior to the occurrence of contamination in one of the steps of a relevant process flow, which is in the danger of the process flow is already contaminated.
In accordance with another aspect of the present invention, an apparatus is provided for finding contamination occurrence in a process flow. Said apparatus comprises at least a memory device and a processor connected to the memory device, wherein a program is stored in the memory device for controlling the processor. Said processor operates according to the program of the memory device to input a tool database in which a plurality of tools are defined or xe2x80x9ctaggedxe2x80x9d by a set of contamination information of the tool database for being either a contaminated tool or an uncontaminated tool. Then a process database including the order of steps in the relevant process flow and a corresponding tool information for each step of the process flow is input to the computer. Said tool information includes at least one tool to be executed during the relevant step of the process flow without including the contamination information of each tool. Finally, the process database associated with the tool database is cross-examined in order to display a contamination warning message prior to the occurrence of contamination in one of the steps of a relevant process flow, which is in the danger of being contaminated if any one of the preceding steps of the process flow is already contaminated.
The major advantage of the above-mentioned method and apparatus according to the present invention is that possible occurrence of contamination in a process flow can be detected and warned well before the actual implementation of the process flow by an automatic system.
In accordance with yet another aspect of the present invention, a contamination prevention system is provided for finding contamination occurrence in a process flow. Said system comprises at least a memory device and a processor. The memory device has a tool database in which a plurality of tools for manufacturing an object are defined. The memory device further includes a process database comprising a plurality of steps in a relevant process flow and a set of object specific information. In particular, the tool database includes a contamination information for each tool to determine whether the relevant tool is a contaminated tool or an uncontaminated tool. The process database comprises a set of tool information for each step of the process flow. The tool information includes at least one tool to be executed during the relevant step of the process flow. The object information includes a contamination tag to indicate whether the object is contaminated or uncontaminated. The processor communicates with the memory device and is configured to initiate a contamination tag to indicate that the object is uncontaminated before the object is sent to experience any process step. If, the object has experienced any process step whose tool information includes at least a contaminated tool, the contamination tag of the object would indicate that the object is contaminated. On the contrary, if the tool information of a succeeding process step indicates an uncontaminated tool and a contaminated object, the object is prohibited from being executed by said process step.
The major advantage of the above method is to prevent a widespread occurrence of contamination during a process of fabricating an object by an automatic system.